This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 6 |
| 5 | 18 |
| 6 | 198 |
| 7 | 6930 |
| 8 | 2737350 |
| 9 | 37936933650 |
| 10 | 207693292716721350 |
| 11 | 15758493330480878908260133650 |
| 12 | 6545866736124132578837836330405530973356721350 |